Tiron™ (trademark of E.I. du Pont de Nemours and Company) is a known chelant. However, it is currently too expensive to make for commercial purposes. For example, in published US 2009/0176684 detergent compositions containing catechols, such as Tiron™ (1,2-dihydroxybenzene-3,5-disulfonic acid), which do not have or do not develop the reddish color associated with the catechol/ferric iron chelate, are disclosed.
Several attempts have been made to prepare Tiron™ or its derivatives but for various reasons, none of these have been commercially practical or cost effective for this purpose. A few of these prior efforts are discussed below.
Some groups have attempted this process using catechol as the starting compound. Cousin, in Compt. Rend. 117, 113 (1893); Bull. Soc. Chim. 11, 103 (1894); and Ann. Chim. 13, 511 (1898), made the free sulfonic acid of Tiron™ using oleum (30%) at 100° C. This process required the use of oleum and elevated temperature. Jakob Pollak and Erich Gebauer-fulnegg, Monatshefte fuer Chemie, 47, 109 (1926) again made the free sulfonic acid of Tiron™ using ClSO3H at RT. This process required the use of a chlorinated reagent.
Rhodia in WO 2007/144344 A1, published 21 Dec. 2007, heated a reaction mixture of catechol in H2SO4 to 85-90° C. to form (Tiron™) disodium salt. However, the free acid of 4,5-dihydroxy-1,3-benzenedisulfonic acid (Tiron™) does not precipitate from the sulfuric acid reaction mixture and neutralization is required in order to precipitate the sodium salt of Tiron™. This leads to a substantial salt waste stream and complicates the task of recycling the H2SO4.
A compound similar to Tiron™, namely a 2,3,4-trihydroxybenzenesulfonic acid, has been made starting with 1,2,3-trihydroxybenzene, which is also known as pyrogallol (PG). The process by Schieff, Ann. 178, 187 (1875) used H2S2O7 at 100° C. This process required the use of pyrosulfuric acid and elevated temperature. Two groups, Delage, Compt. Rend. 131, 450 (1900); 133, 298 (1901); 136, 760, 893, 1202 (1903) and Anschutz, Ann. 415, 87 (1918), tried this process using H2SO4 at 100° C. These processes required elevated temperature and produced a mixture of products.
Two groups, Delage, Compt. Rend. 132, 421 (1901); and Pollak, Gebauer-fulnegg, and Litvay, Monatshefte fuer Chemie, 47, 537 (1927), used PG as the starting material to make 4,5,6-trihydroxy-1,3-benzenedisulfonic acid, using H2SO4 at 100° C. This process required elevated temperature.
Clearly, it would be advantageous to have a cost effective and practical approach using renewable biomass resources to make such additives.